Detection and quantification of microscopic particles in bodily fluids, such as white blood cells, bacteria, and viruses, as well as other analytes, such as proteins, enzymes and metabolites, is important in diagnosing and treating many conditions that impair human health. For example, identifying CD4 T-cell counts in patients provide physicians with information of the patient's HIV infection status. Healthcare providers often take multiple CD4 T-cell counts over time in order to determine the progression of the disease and the effectiveness of HIV treatments. A falling CD4 T-cell count indicates that HIV is progressing and damaging the immune system, whereas a rising CD4 T-cell count indicates that HIV treatments are altering the course of the disease.